DTV television transmitter/receiver and method of processing data in DTV transmitter/receiver

ABSTRACT

A DTV transmitter includes a pre-processor pre-processing enhanced data, a data formatter generating enhanced data packets including known data, a multiplexer multiplexing the enhanced data packets with main data packets, a data randomizer randomizing the multiplexed data packets, an RS encoder RS-encoding the randomized data packets, and a data interleaver interleaving the RS-coded data packets, where a plurality of known data sequences are included in the interleaved enhanced data packets. Finally, the DTV transmitter further includes an enhanced encoder which codes each block of enhanced data placed between any two of the known data sequences and bypasses the interleaved main data packets.

CROSS-REFERENCE TO RELATED APPLICATIONS

More than one reissue application has been filed for the reissue of U.S.Pat. No. 8,149,941. The reissue applications are application Ser. Nos.14/244,740 filed Apr. 3, 2014 (now U.S. Pat. No. RE45,736), 14/445,888filed Jul. 29, 2014 (a continuation reissue application of reissueapplication Ser. No. 14/244,740), 15/286,190 filed Oct. 5, 2016 (thepresent application, a continuation reissue application of reissueapplication Ser. No. 14/445,888), all of which are reissues of U.S. Pat.No. 8,149,941. This application is a continuation reissue application ofU.S. Reissue application Ser. No. 14/445,888 filed on Jul. 29, 2014,which is a continuation reissue application of U.S. Reissue applicationSer. No. 14/244,740 filed on Apr. 3, 2014, issued as U.S. Pat. No.RE45,736 on Oct. 6, 2015, which is a reissue application of U.S. Pat.No. 8,149,941 issued from U.S. patent application Ser. No. 13/196,773filed on Aug. 2, 2011, which is a continuation of U.S. patentapplication Ser. No. 13/053,146, filed on Mar. 21, 2011 (and issued asU.S. Pat. No. 8,014,459 on Sep. 6, 2011), which is a continuation ofU.S. patent application Ser. No. 11/514,125, filed on Aug. 30, 2006 (andissued as U.S. Pat. No. 7,936,837 on May 3, 2011), which claims thebenefit of earlier filing date and right of priority to Korean PatentApplication No. 10-2006-0006517, filed on Jan. 20, 2006, the contents ofall of which are hereby incorporated by reference herein in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital communication system, andmore particularly, to a digital television (DTV) transmitter/receiverand a method of processing data in the DTV transmitter/receiver.

2. Discussion of the Related Art

Generally, the 8T-VSB transmission system adopted as a digitalbroadcasting standard by Korea and North America is a digital broadcastsystem developed for MPEG video/audio data transmission.

As the digital signal processing technology rapidly develops with theglobal use of Internet, the tendency for combining digital homeappliances, computer and Internet together rises. So, in order to meetthe user's various demands, many efforts need to be made to develop asystem capable of transmitting various supplemental data withvideo/audio data.

A user of supplemental data broadcasting is expected to use thesupplemental data broadcasting using a PC card or portable device havinga simple type indoor antenna attached thereto.

Yet, signal intensity can be considerably decreased due to a shieldeffect of a wall and an influence of a near moving object within anindoor space and broadcast receiving performance can be reduced due to aghost and noise generated from a reflective wave. Unlike a case ofgeneral video/audio data, a case of supplemental data transmissionshould have a lower error rate. In case of the video/audio data, anerror failing to be detected by human eyes/ears does not matter. Yet, incase of supplemental data (e.g., a program execution file, stockinformation, etc.), a 1-bit error can cause a serious problem. So, thedemand for developing a system more persistent against ghost and noisegenerated from a channel rises.

Supplemental data transmission will be performed by time-divisionthrough the same channel of MPEG video/audio in general. Since thebeginning of digital broadcasting, ATSC VSB digital broadcast receiversreceiving the MPEG video/audio only have globally spread in markets. So,the supplemental data transmitted on the same channel of the MPEGvideo/audio should avoid causing any effect to the conventional ATSC VSBdedicated receiver previously supplied to the markets. Such a situationis defined as ATSC VSB compatibility. And, a supplemental data broadcastsystem should be compatible with the ATSC VSB system. Besides, thesupplemental data could be called enhanced data or E-VSB data.

However, in a poor channel environment, reception performance of theconventional ATSC VSB reception system may be reduced. Specifically, aportable or mobile receiver needs higher robustness against a channelchange and noise.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a digital broadcastsystem which is suitable for transmission of supplemental data andresistant against noise that substantially obviates one or more problemsdue to limitations and disadvantages of the related art.

An object of the present invention is to provide a digital broadcastsystem and a processing method, which are capable of inserting knowndata, which is previously known in transmitting/receiving ends, into acertain region of data interval to transmit it thereto, therebyenhancing receiving performance.

Another object of the present invention is to provide a digitalbroadcast system and a processing method, which are capable ofperforming added block encoding/decoding for enhanced data, therebyenhancing transmitting/receiving performance.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, adigital television (DTV) transmitter for processing main and enhanceddata for transmission includes a pre-processor for pre-processing theenhanced data by coding the enhanced data for forward error correction(FEC) and expanding the FEC-coded enhanced data, a data formatter forgenerating enhanced data packets including the pre-processed enhanceddata and for inserting known data into the enhanced data packets, and afirst multiplexer for multiplexing the enhanced data packets with maindata packets including the main data.

The DTV transmitter may further include a data randomizer forrandomizing the multiplexed enhanced and main data packets, a first RSencoder for RS-coding the randomized data packets by adding firstsystematic parity data to each main data packet and adding first RSparity place holders to each enhanced data packet, and a first datainterleaver for interleaving the RS-coded main and enhanced datapackets, where the interleaved enhanced data packets include a pluralityof known data sequences.

The DTV transmitter may further include an enhanced encoder for codingeach block of enhanced data placed between any two of the known datasequences in the interleaved enhanced data packets and bypassing theinterleaved main data packets. Two known data sequences which confineeach block of enhanced data may be consecutive or non-consecutive.

In one example, The enhanced encoder may include a demultiplexer fordemultiplexing the interleaved main and enhanced data packets, a blockencoder for encoding each block of enhanced data placed between any twoof the known data sequences in the demultiplexed enhanced data packets,a buffer for temporarily storing the demultiplexed main data, and asecond multiplexer for multiplexing the encoded block of enhanced dataand the main data stored in the buffer.

In another example, the enhanced encoder may include a demultiplexer fordemultiplexing the interleaved main and enhanced data packets, an N-wayinterleaver for dividing each block of enhanced data placed between anytwo of the known data sequences in the demultiplexed enhanced datapackets into N sub-blocks of enhanced data, a plurality of sub-blockencoders for encoding the sub-blocks of enhanced data, respectively, adeinterleaver for deinterleaving the encoded sub-blocks of enhanceddata, a buffer for temporarily storing the demultiplexed main data, anda second multiplexer for multiplexing the encoded sub-blocks of enhanceddata and the main data stores in the buffer.

The DTV transmitter according to the present invention may furtherinclude a data deinterleaver for de-interleaving the data packetsoutputted from the enhanced encoder, and an RS parity remover forremoving the first systematic parity data and the first RS parity placeholders from the de-interleaved main and enhanced data packets. The DTVtransmitter may further include a second RS encoder for RS-coding thedeinterleaved main and enhanced data packets by adding second systematicparity data to each deinterleaved main data packet and adding second RSparity holders to each de-interleaved enhanced data packet, and a seconddata interleaver for interleaving the main and the enhanced data packetsoutputted from the second RS encoder.

In addition, the DTV transmitter may further include a byte-symbolconverter for converting the data packets outputted from the second datainterleaver into symbols, and a trellis encoder for trellis-encoding theconverted symbols. The trellis encoder is initialized when the symbolsrepresent a beginning of a known data sequence. The DTV transmitter mayfurther include an initialization controller for generatinginitialization data symbols required to initialize one or more memoriesincluded in the trellis encoder, and a second multiplexer for outputtingthe initialization data symbols to the trellis encoder when the symbolsrepresent the beginning of the known data sequence.

Furthermore, the DTV transmitter may further include abackward-compatibility processor for generating new parity symbols basedon an output of the second RS encoder and the initialized data symbolsand providing the new parity data symbols to the second multiplexer,which outputs the new parity symbols to the trellis encoder when thesymbols outputted from the byte-symbol converter represent the second RSparity place holders.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a schematic block diagram of a digital broadcasttransmitting system according to an embodiment of the present invention;

FIG. 2 illustrates a detailed block diagram of a Trellis encoder of FIG.1, according to an embodiment of the present invention;

FIG. 3 illustrates a schematic block diagram for a structure of a datainterleaver of FIG. 1;

FIG. 4 illustrates a view for describing a sequence of output of a datainterleaver in the VSB frame;

FIG. 5A illustrates data configuration at the input end of the datainterleaver as known data is inserted thereto, according to the presentinvention;

FIG. 5B illustrates data configuration at the output end of the datainterleaver as known data is inserted thereto, according to the presentinvention;

FIG. 6A illustrates a schematic block diagram of an embodiment of theE-VSB enhanced encoder according to the present invention;

FIG. 6B illustrates a schematic block diagram of another embodiment ofthe E-VSB enhanced encoder according to the present invention;

FIG. 7A illustrates a schematic block diagram of an embodiment of theE-VSB enhanced decoder according to the present invention;

FIG. 7B illustrates a schematic block diagram of another embodiment ofthe E-VSB enhanced decoder according to the present invention; and

FIG. 8 illustrates a schematic block diagram of a digital broadcastreceiving system according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

The terminologies disclosed the present application are widely used inthis fields of the present invention. However, some of them are definedby the inventors. In this case, the newly defined terminologies aredescribed in detail in the following description. Therefore, theterminologies in the present invention will be understood on the basisof the disclosure of the present application.

Enhanced data in the present application may be any of applicationprogram execution files, data having information, such as stockinformation, etc., and video/audio data. Known data may be data which ispreviously known in transmitting/receiving ends, based on a protocol.Main data is indicative of data which can be received by theconventional receiving systems, including video/audio data.

The present invention serves to multiplex the enhanced data havinginformation and the known data known in the transmitting/receiving ends,and to transmit them, to enhance receiving performance of a receiver.

Especially, the present invention serves to initialize a memory in aTrellis encoder at the beginning portion of the known data stream, andapply a block encoding for the enhanced data at thetransmitting/receiving ends, using the initialization characteristics,to perform additional encoding/decoding.

FIG. 1 illustrates a schematic block diagram of a digital broadcasttransmitting system according to an embodiment of the present invention.The digital broadcast transmitting system includes an E-VSB preprocessor101, an E-VSB packet formatter 102, a packet multiplexer 103, a datarandomizer 104, a scheduler 105, an E-VSB post-processor 110, an RSencoder/Non-systematic RS parity holder inserter 121, a data interleaver122, a Trellis encoding unit 123, a compatible processor 130, a framemultiplexer 140, and a transmitting unit 150.

Main data is outputted to the multiplexer 103, based on transport packetunits. Enhanced data is outputted to the E-VSB preprocessor 101. TheE-VSB preprocessor 101 performs pre-processes, such as additional errorcorrection code, interleaving, insertion of null data, etc., regardingthe enhanced data, and then outputs it to the E-VSB formatter 102.

The E-VSB packet formatter 102 includes at least one of the preprocessedenhance data and predetermined known data (or known data place holder),under control of the scheduler 105, and adds a 4-byte MPEG headerthereto to form a MPEG packet based on 188 bytes. After that, the MPEGpacket is outputted to the packet multiplexer 103.

The packet multiplexer 103 serves to perform time multiplexing, based ontransport stream (TS) packet unit, for the main data packets and theenhanced data packet, according to pre-defined multiplexing method,under the control of the scheduler 105. Here, the main data packets andthe enhanced data packet are formed on the basis of 188 byte unit.

Namely, the scheduler 105 generates a control signal such that thepacket multiplexer 103 multiplexes main data packets and enhanced datapackets, and then output them to the packet multiplexer 103. The packetmultiplexer 103 receiving the control signal multiplexes the main datapackets and the enhanced data packets, based on TS packet units, andoutputs the multiplexed result.

The output of the packet multiplexer 103 is inputted to the datarandomizer 104. The data randomizer 104 removes an MPEG synchronous bytefrom the input packet and randomizes the remaining 187 bytes usingpseudo random bytes, which are generated therein, to output them to theE-VSB post-processor 110.

The E-VSB post-processor 110 includes an RS encoder/Non-systematic RSparity place holder inserter 111, a data interleaver 112, an E-VSBenhanced encoder 113, a data de-interleaver 114, and an RS byte remover115.

The RS encoder/Non-systematic RS parity place holder inserter 111performs a systematic RS encoding or a non-systematic RS parity holderinsertion for the randomized data.

Namely, when the 187 byte packet, which is outputted from the datarandomizer 104, is main data packet, the RS encoder/Non-systematic RSparity place holder inserter 111 performs systematic RS encoding, whichis identical to that of a conventional ATSC VSB system, and adds aparity of 20 bytes to the end of the 187 byte data, to output it to thedata interleaver 112.

On the other hand, when the 187 byte packet, which is outputted from thedata randomizer 104, is enhanced data packet, the RSencoder/Non-systematic RS parity place holder inserter 111 inserts RSparity place holder, which is composed of null data of 20 bytes, in thepacket, and inserts data of the enhanced data packet to places of theremaining 187 byte packet, correspondingly, to output them to the datainterleaver 112.

The data interleaver 112 performs data interleaving for the output ofthe RS encoder/Non-systematic RS parity place holder inserter 111 tooutput it to the E-VSB enhanced encoder 113.

The E-VSB enhanced encoder 113 performs additional ½ encoding for onlythe enhanced data, which is outputted from the data interleaver 112, tooutput it to the data de-interleaver 114. The data de-interleaver 114performs data de-interleaving for the inputted data to output it to theRS byte remover 115. Here, the data de-interleaver 114 performs areverse process of the data interleaver 112.

Data interleaving of the data interleaver 112 and encoding of the E-VSBenhanced encoder 113 will be described later.

The RS byte remover 115 removes the 20 byte parity which is added in theRS encoder/Non-systematic RS parity place holder inserter 111. Here,when the inputted data is main data packet, the last 20 bytes of the 207bytes are removed. When the inputted data is the enhanced data packet,parity place holders of 20 bytes of 207 bytes are removed, in which theparity place holders are inserted thereto to perform non-systematic RSencoding. Namely, such procedures for the enhanced data serve tore-calculate parity because original data is changed by the E-VSBenhanced encoder 113.

The output of the RS byte remover 115 is inputted to the RSencoder/Non-systematic RS parity holder inserter 121. When the 187 bytepacket, which is outputted from the RS byte remover 115, is main datapacket, similar to the RS encoder/Non-systematic RS parity place holderinserter 111, the RS encoder/Non-systematic RS parity holder inserter121 performs systematic RS encoding, which is identical to aconventional ATSC VSB system, and inserts parity of 20 bytes to the endof the data of 187 bytes.

When the packet is enhanced data packet, byte places of 20 parities aredetermined in the packet to perform non-systematic RS encoding in therear end of the compatible processor 130. After that, parities obtainedafter non-systematic RS encoding may be inserted in the determined byteplaces of parities or null byte instead of the parities may be insertedthereto. The bytes in the enhanced data packet are sequentially insertedin the places of the remaining 187 bytes. The null byte is determined bya certain value. The null byte is substituted with a parity value whichis calculated in the non-systematic RS encoder 133 of the compatibleprocessor 130.

Therefore, the null byte serves to secure a place of parity byte ofnon-systematic RS code. The output of the RS encoder/Non-systematic RSparity holder inserter 121 is outputted to the data interleaver 122.Also, when the packet is enhanced data packet, the output is inputted tothe compatible processor 130 to re-calculate parity.

The data interleaver 122 performs interleaving for the inputted data,like the interleaving rule of data interleaver 112.

FIG. 3 illustrates a schematic block diagram for a structure of a datainterleaver (122 or 112) of FIG. 1, or a convolution interleaver ofwhich branch number is 52 and the number M of a unit memory byte is 4.

As shown in FIG. 3, when a first byte is inputted thereto, it isoutputted through the first branch, and a second byte is inputtedthereto through a second branch. Therefore, a value before 52*4 bytes isoutputted.

FIG. 4 illustrates a view for describing a sequence of output of a datainterleaver of FIG. 3 in the VSB frame. The data is sequentiallyinputted from the lower part to the upper part, based on segment units,in which bytes in the segment are sequentially inputted thereto fromleft to right. The numerals of FIG. 4 are indicative of the outputsequence of the data interleaver. The data interleaver is operated onthe basis of unit of 52 segments.

The output of the data interleaver 122 is inputted to the Trellisencoding unit 123. The Trellis encoding unit 123 encodes the inputted 2bits to 3 bits to output it thereto. The output of the Trellis encodingunit 123 is inputted to the frame multiplexer 140. The frame multiplexer140 inserts a field synchronization bit and a segment synchronizationbit to the output of the Trellis encoding unit 123 to transmit it to thetransmitting unit 150. The transmitting unit 150 includes a pilotinserter 151, a VSB modulator 152, and an RF converter 153. Since thetransmitter unit 150 is operated as the conventional VSB transmitter,its detailed description will be omitted.

In order to use the output data of the Trellis encoding unit 123 as theknown data which was defined in the transmitting/receiving ends, it isnecessary to initialize a memory of the Trellis encoding unit 123 beforethe known data inserted in the enhanced data packet is processed. Theinput of the Trellis encoding unit 123 is needed to perform substitutionfor the initialization. RS parity affected by the changed data isre-calculated to be substituted with the original parity data. Such aprocedure is performed in the compatible processor 130.

FIG. 2 illustrates a detailed block diagram of a Trellis encoding unit123 of FIG. 1, which is initializable.

The Trellis encoding unit 123 which is initializable includes abyte-symbol converter 201, a multiplexer 202 for selecting one of inputsthereof, a Trellis encoder 203 for inputting the selected input from themultiplexer 202, and a Trellis state initialization controller 204 forinitializing the Trellis encoder 203.

Such Trellis encoding unit is operated as follows. The byte-symbolconverter 201 inputs interleaved data based on byte units to convert itto interleaved data based on symbol units, and then performs 12-wayinterleaving for the data to output it to the multiplexer 202.

For a normal case, the output of the byte-symbol converter 201 isselected by the multiplexer 202 such that the output can be transmittedto the Trellis encoder 203 through the multiplexer 202. On the otherhand, when the interleaved data is known data and the known data is thebeginning portion of the successively inputted known data stream, it isnecessary to initialize the Trellis encoder 203, since the Trellisencoder 203 has a memory and thus its present output is affected bypresent and past inputs. Therefore, in order to output a predeterminedsignal at a certain time, the memory of the Trellis encoder 203 must beinitialized at a certain value.

When the memory of the Trellis encoder 203 requires initializationthereof, a part of the known data is substituted with an initializationdata to be outputted to the Trellis encoder 203. Afterwards, the memoryof the Trellis encoder 203 is initialized to a predetermined value basedon the initialization data. Therefore, from the time point of theinitialization, the output of the Trellis encoder 203 can be the knowndata which is encoded to comply with the transmitting/receiving ends.

The Trellis state initialization controller 204 for initializing theTrellis encoder 203 inputs a memory value of the Trellis encoder 203 togenerate initialization data to be inputted to the Trellis encoder 203and then outputs it to the compatible processor 130.

Namely, the Trellis encoder 203 is operated such that upper bit of thetwo bits composing a symbol is encoded to a single bit using a singlememory to be outputted, and the lower bit is encoded to two bits usingthe two memories to be outputted. Here, when the input data is knowndata and thus the known data is the beginning of the successivelyinputted known data stream, the memories must be initialized to outputthe inputted data as desired known data, after the inputted dataunder-goes Trellis encoding. Therefore, when the memory of the Trellisencoder 203 requires initialization, the Trellis state initializationcontroller 204 generates initialization data according to a presentstate and a desired initialization state of the memory, and then outputsit to the multiplexer 202.

The initialization data is formed by 4 bits, or two symbols. Here, theremay be a plurality of the Trellis encoder 203, for example, 12. The 12bytes outputted from the multiplexer 202 are sequentially inputted tothe each of the Trellis encoders 203. Here, the beginning 4 bits of eachbyte, or two symbols, can be initialization data. Namely, theinitialization controller 204 generates initialization data and thenoutputs it to the multiplexer 202 and the compatible processor 130, inwhich the initialization data initializes the memory of the Trellisencoder 203 in first two symbol intervals at which the known data symbolstream is started.

The compatible processor 130 inputs the output of the RSencoder/Non-systematic RS parity holder inserter 121 and the output ofthe initialization controller 204 and then generates non-systematic 20byte parity to be outputted to the multiplexer 202 of the Trellisencoding unit 123.

Namely, since the memory of the Trellis encoding unit 123 is initializedby new data but not by data which is interleaved in the data interleaver122, RS parity must be re-generated to substitute the original paritydata. Such procedure is performed in the compatible processor 130.

The compatible processor 130 includes a packet buffer 131, a symbol-byteconverter 132, a non-systematic RS encoder 133, and a byte-symbolconverter 134.

Namely, the output of the RS encoder/Non-systematic RS parity holderinserter 121 is inputted to the data interleaver 122 and the packetbuffer 131. The initialization data of the initialization controller 204is inputted to the multiplexer 202 of the Trellis encoding unit 123 andthe symbol-byte converter 132 of the compatible processor 130.

Here, since the RS encoder/Non-systematic RS parity holder inserter 121inputs and outputs its input and output based on byte unit, thesymbol-byte converter 132 converts the initialization data of symbolunit to the initialization of byte unit and then outputs it to thepacket buffer 131.

The packet buffer 131 inputs the byte output from the RSencoder/Non-systematic RS parity holder inserter 121 and the byte outputfrom the symbol-byte converter 132 to temporarily store them and thenoutputs them to the non-systematic RS encoder 133. The non-systematic RSencoder 133 inputs the byte output from the packet buffer 131 togenerate parity of non-systematic 20 bytes and then outputs the paritybased on symbol unit to the multiplexer 202 of the Trellis encoding unit123 through the byte-symbol converter 134.

When the inputted data, which is interleaved and then converted tosymbols, is the beginning of known data stream, the multiplexer 202selects the initialization symbol of the initialization controller 204instead of the inputted symbol, and then outputs it. When the inputteddata is RS parity or parity place holder, the multiplexer 202 selectsthe output symbol of the symbol-byte converter 134 of the compatibleprocessor 130 instead of the inputted symbol. Except for the abovecases, the multiplexer 202 selects inputted data, which is interleavedand then converted to symbol, and then outputs it to the Trellis encoder203. Namely, substitution of initialization symbol occurs at places offirst two symbols in the known data stream, to be inputted to theTrellis encoder 203. Also, substitution of parity symbol, which isre-calculated in the compatible processor 130, occurs at the parityplace of each packet, to be outputted to the Trellis encoder 203.Especially, when the RS encoder/Non-systematic RS parity holder inserter121 does not insert a non-systematic RS parity to the enhanced datapacket but instead inserts a null byte, the compatible processor 130calculates non-systematic RS parity of the enhanced data packet,regardless of initialization of the Trellis encoder, to performsubstitution using the calculation result.

The Trellis encoder 203 performs Trellis encoding for the data outputtedfrom the multiplexer 202, based on symbol unit, and then outputs it tothe frame multiplexer 140. Also, the Trellis encoder 203 outputs itsmemory state to the initialization controller 204.

Known Data Insertion and Non-systematic RS Parity Place

The following is a description for insertion of known data and settingof a non-systematic RS parity place.

FIG. 5A illustrates data configuration at the input end of the datainterleaver as known data is inserted thereto. FIG. 5B illustrates dataconfiguration at the output end of the data interleaver as the data ofFIG. 5A is inserted thereto.

Namely, a receiver sequentially inputs data from the output end of thedata interleaver outputted as the data interleaver output. Also, knowndata must be successively inputted thereto in response to the sequenceof number of FIG. 4, such that the receiver can receive timelysuccessive known data. As shown in FIG. 5B, in order that a single datasegment, which is received in the receiver, is all known data, thesingle data segment is divided into 52 byte units, as shown in FIG. 5A.Afterwards, the known data is inserted thereto at a place of datasegment at each 52 byte unit. Here, the beginning part of the known datastream needs initialization byte. Therefore, when the place of knowndata is determined in the data segment, a place of the initializationbyte is determined as the place at which normal data ends and the knowndata is started, from the point of view of the output end of the datainterleaver. When the place of initialization byte of the known data isdetermined, the place of a non-systematic RS parity byte can bedetermined. The place is preferably located such that the parity bytescan be outputted latter than the initialization bytes, from the point ofview of the output end of the data interleaver. Namely, for a singlesegment, as shown in FIG. 4, the lower order bit is outputted earlierfrom the data interleaver than the larger one. Therefore, the RS parityis preferably located later than the sequence number of theinitialization bytes.

The following is another embodiment of a method for inserting known datathereto. As shown in FIG. 5B, when the known data is inserted after theMPEG header in a first segment, from the point of view of the output endof the data interleaver, or the known data is inserted from after theMPEG header to the end of the segment, since MPEG header bytes of asecond segment have a certain value for enhanced data packets, the MPEGheader bytes can be regarded as continuation data.

As such, the present invention serves to perform substitution of data toinitialize the memory of the Trellis encoder to a predetermined initialstate when the known data stream is started. Also, the present inventionserves to perform non-systematic RS encoding for enhanced data packetsto keep compatibility with conventional receivers by the substituteddata or to insert known data in conventional systematic RS parityregions.

E-VSB Enhanced Encoder

On the other hand, the E-VSB enhanced encoder 113 performs additionalencoding for enhanced data and then outputs it thereto. Namely, when theoutput of the data interleaver 112 is main data, the E-VSB enhancedencoder 113 does not change MPEG header byte, which is added in theE-VSB packet formatter 102, or RS parity or RS parity place byte, whichare added to the enhanced data packet in the RS encoder/Non-systematicRS parity place holder inserter 111, and outputs them thereto.

Also, similar to main data, the known data is outputted thereto withoutadditional encoding procedure. However, the method for processing theknown data may be different from that for processing the main data.

For example, there is a method for outputting known data which isgenerated in a symbol region, instead of a known data place holder, inthe E-VSB enhanced encoder 113, in a state where the known data placeholder is inserted in the E-VSB packet formatter 102. Also, there isanother method in which the E-VSB enhanced encoder 113 does not changedata but outputs the data, in state where the known data is inserted inthe E-VSB packet formatter 102.

The former method is described through FIG. 6A and FIG. 7a, and thelatter method is described through FIG. 6B and FIG. 7B.

Firstly, as shown in FIG. 6A, the E-VSB enhanced encoder 113 includes ademultiplexer 610, a buffer 620, a U/C encoding unit 630, and amultiplexer 640.

The U/C encoding unit 630 serves to encode U bit of the enhanced data toC bit and then to output it thereto. For example, when 1 bit of theenhanced data is encoded to two bits to output it thereto, U is 1 and Cis 2.

The U/C encoding unit 630 includes a byte-bit converter 631, a U/Cencoder 632, a block interleaver 633, and a bit-byte converter 634. TheU/C encoder 632 is implemented with a 1/2 encoder. The U/C encoder 632and the block interleaver 633 (which is optional) are defined as an“enhanced encoder core” in the present invention.

As shown in FIG. 7A, the demultiplexer 610 outputs its output to thebuffer 620 when inputted data is main data, and to the U/C encoding unit630 when the inputted data is enhanced data.

The buffer 620 delays main data for a certain time, and then outputs itto the multiplexer 640. Namely, when main data is inputted to thedemultiplexer 610, the buffer 620 is used to compensate time delay whichis generated while the enhanced data is additionally encoded.Afterwards, the main data, whose time delay is controlled by the buffer620, is transmitted to the data deinterleaver 114 through themultiplexer 640.

When the known data is inputted, the known data place holder is insertedthereto in the E-VSB packet formatter 102. The multiplexer 640 of theE-VSB enhanced encoder 113 selects the training sequence T instead ofthe known data place holder and then outputs it thereto. Therefore, theknown data can be outputted without additional encoding.

On the other hand, the byte-bit converter 631 of the U/C encoding unit630 converts the enhanced data byte to enhanced data bits and thenoutputs them to the 1/2 encoder 632. The 1/2 encoder 632 encodesinputted one bit to two bits to output them thereto.

The 1/2 encoder 632 is implemented with a convolution encoder or a lowdensity parity check (LDPC) encoder, etc., which can use block codes.Also, the 1/2 encoder 632 may selectively adopt a block interleaver 633according to implementation objectives.

For example, assuming that one byte of the enhanced data is extended totwo bytes as null bits are inserted among bits thereof in the E-VSBpre-processor 101. The byte-bit converter 631 removes the null bits ofinputted bytes and then outputs only effective data bits to the 1/2encoder 632.

The 1/2 encoder 632 encodes one bit input to two bits, on the basis ofblock coding, and the block interleaver 633 inputs the two bits toperform block interleaving therefor.

The block interleaving is related to the total system performance andmay be used in any interleavings, such as a random interleaving.

Here, the 1/2 encoder 632 performs encodings based on block units. Theblock size must be determined such that the block interleaver 633 canperform block interleaving.

According to the present invention, the block size can be determined byinput format of the E-VSB enhanced encoder 113, as shown in FIG. 5B.

The following is a description for a method for determining block sizewith reference to the input format of FIG. 5B.

FIG. 5B shows that the number of parts to initialize the memory ofTrellis encoder is 5 when interleaving unit is 52 segments. In thiscase, it can be divided from one block into four blocks.

Namely, for high block code performance of FIG. 5B, the block size canbe preferably determined by the bit number of the enhanced data fromfirst Trellis initialization to fifth Trellis initialization.

According to another embodiment, the block size can be determined by thebit number of the enhanced data from among the first Trellisinitialization to third Trellis initialization. In this case, theenhanced data of one data interleaving unit, which must be encoded inthe E-VSB enhanced encoder 113, is divided into two blocks and thenencoded. Namely, the enhanced data among the first Trellisinitialization and third Trellis initialization is encoded on the basisof one block size, and the enhanced data among the third Trellisinitialization and the fifth initialization is encoded on the basis ofanother block size.

Also, according to a further embodiment, the block size can bedetermined as the bit number of the enhanced data between the firstTrellis initialization and the second Trellis initialization. In thiscase, the enhanced data of one data interleaving unit, which must beencoded in the E-VSB enhanced encoder 113, is divided into four blocksand then encoded.

The enhanced data, which was used to determine the block size, must beadditionally encoded in the E-VSB enhanced encoder 113. Here, theenhanced data does not include the known data and non-systematic RSparity.

The block size can be set with reference to the Trellis initialization,since data after Trellis initialization is not affected by inputs beforethe initialization. Namely, since the enhanced data have limited lengthswith reference to the data of the Trellis initialization, start and endof classified blocks are determined. Therefore, encoding performance ofthe enhanced data, which is performed in the block coding, can befurther increased.

The bit-byte converter 634 serves to convert output bits of the blockinterleaver 633 to bytes and then outputs them to the multiplexer 640.

The multiplexer 640 selects main data outputted from the buffer 620,when the inputted data is main data, and enhanced data, which is encodedin the U/C encoding unit 630, when the inputted data is the enhanceddata. Also, when the inputted data is known data place holder, themultiplexer 640 selects training sequence to output it to thedeinterleaver 114.

FIG. 6A illustrates a schematic block diagram of an embodiment of theE-VSB enhanced encoder, and FIG. 6B illustrates a schematic blockdiagram of another embodiment of the E-VSB enhanced encoder. FIG. 6A andFIG. 6B are different from one another, regarding a known dataprocessing part. Namely, FIG. 6B is identical to FIG. 6A except that,when the inputted data is known data, the demultiplexer 660 outputs theknown data to the buffer 670 such that the buffer 670 can delay acertain time and then output it to the deinterleaver 114 through themultiplexer 680. Therefore, the detailed description for FIG. 6B will beomitted.

Such processes are performed under the assumption that the known data isalready inserted in the enhanced data packet in the E-VSB packetformatter 102.

As such, the present invention serves to initialize the memory of theTrellis encoder at the beginning part of the know data stream andperform additional encoding for the enhanced data, based on blockcoding, using the initialization. Therefore, performance of theadditional encoding for the enhanced data can be increased.

FIG. 7A illustrates a schematic block diagram of an embodiment of theE-VSB enhanced decoder 113, and FIG. 7B illustrates a schematic blockdiagram of another embodiment of the E-VSB enhanced decoder 113.

Firstly, as shown in FIG. 7A, the E-VSB enhanced encoder 113 includes ademultiplexer 710, a buffer 720, an N-way encoder 730, and a multiplexer740.

The N-way encoder 730 includes an N-way interleaver 731, an N-waydeinterleaver 733 and N enhanced encoding units 7321˜732N, which areconnected, in parallel, between the N-way interleaver 731 and the N-waydeinterleaver 733.

Each enhanced encoding unit includes a symbol-bit converter, an enhancedencoder core, and a bit-symbol converter. The enhanced encoder coreincludes a U/C encoder and a block interleaver. The U/C encoder ispreferably implemented with a 1/2 encoder. The 1/2 encoder may use blockcodes of a convolution encoder or a low density parity check (LDPC)encoder. Also, the 1/2 encoder may selectively use a block interleaveraccording to implementation objectives.

As shown in FIG. 7A, when the inputted data is main data, thedemultiplexer 710 outputs the main data to the buffer 720. When theinputted data is enhanced data, the demultiplexer 710 outputs theenhanced data to the N-way interleaver 731 of the N-way encoding unit730.

The buffer 720 delays main data for a certain time, and then outputs itto the multiplexer 740. Namely, when main data is inputted to thedemultiplexer 710, the buffer 720 is used to compensate time delay whichis generated while the enhanced data is additionally encoded.Afterwards, the main data, whose time delay is controlled by the buffer720, is transmitted to the data deinterleaver 114 through themultiplexer 740.

When the known data is inputted, the known data place holder is insertedthereto in the E-VSB packet formatter 102. The multiplexer 740 of theE-VSB enhanced encoder 113 selects the training sequence T instead ofthe known data place holder and then outputs it thereto. Therefore, theknown data can be outputted without additional encoding.

On the other hand, the N-way interleaver 731 converts the enhanced databytes to symbols, such that each of the symbols can be distributed tocorresponding enhanced encoding unit. Namely, the enhanced data of thedemultiplexer 710 are formed into N divided symbol outputs by the N-wayinterleaver 731 of the N-way encoding unit 730.

The N divided symbols are sequentially distributed to the N enhancedencoding units or non-sequentially distributed to the encoding unitsbased on a pre-set interleaving sequence.

For example, when N is 4, one byte is changed to 4 symbols. Therefore,the 4 symbols are distributed to the four enhanced encoding units, insequence or in a predetermined interleaving sequence. Also, symbolslocated at the same places in each of the four bytes are distributed to4 enhanced encoding units based on a predetermined sequence.

The enhanced encoding units have the same structure, such that they canoperate identically.

Therefore one of the enhanced encoding units will be described indetail. Namely, the symbol-bit converter in the enhanced encoding unitinputs a symbol distributed from the N-way interleaver 731 to convert itto bits. Afterwards, a null bit of the bits is removed, such that onlyeffective data bits can be outputted to the enhanced encoder core, inwhich the null bit is inserted thereto through null extension in theE-VSB pre-processor 101.

For example, let's assume that on byte of enhanced data is extended totwo bytes as null bits are inserted among bits in the E-VSBpre-processor 101. Then, the symbol-bit converter removes the null bitsand outputs only effective data bits.

The 1/2 encoder in the enhanced encoder core encodes one bit of input totwo bits, based on block coding, and then outputs them thereto. Theblock interleaver inputs the output of the 1/2 encoder to perform blockinterleaving.

Here, the block size for block coding or block interleaving isdetermined as the block size defined in FIG. 6A and FIG. 6B is dividedby the number of ways N of N-way interleaving. For example, the largestblock size can be determined as the bit number of effective enhanceddata is divided by N, in which the effective enhanced data is locatedamong the first initialization to the last fifth initialization, ofTrellis initialization to form known data as shown in FIG. 5B. On theother hand, as described above, block interleaving having the block sizemay be used in any interleaving operations is related to the totalsystem performance and may be used in any interleavings, such as arandom interleaving.

The output of the enhanced encoder core is converted to symbols in thebit-symbol converter and then outputted to the N-way deinterleaver 733.The N-way deinterleaver 733 performs deinterleaving for the symbolsoutputted from the respective enhanced encoding units and then outputsthem to the multiplexer 740. Here, the N-way deinterleaver 733 performsa reverse operation of the N-way interleaver 731.

When inputted data is main data, the multiplexer 740 selects the maindata outputted from the buffer 720. When the inputted data is enhanceddata, the multiplexer 740 selects the enhanced data outputted from theN-way encoding unit 730. Also, when the inputted data is known dataplace holder, the multiplexer 740 selects training sequence to output itto the data deinterleaver 114.

FIG. 7A and FIG. 7B are different from one another, regarding a knowndata processing part. Namely, FIG. 7B is identical to FIG. 7A exceptthat, when the inputted data is known data, the demultiplexer 760outputs the known data to the buffer 770 such that the buffer 770 candelay a certain time and then output it to the deinterleaver 114 throughthe multiplexer 780. Therefore, the detailed description for FIG. 7Bwill be omitted.

Such processes are performed under the assumption that the known data isalready inserted in the enhanced data packet in the E-VSB packetformatter 102.

FIG. 8 illustrates a schematic block diagram of a digital broadcastreceiving system according to an embodiment of the present invention, inwhich the digital broadcast receiving system receives data, which aretransmitted from the digital broadcast transmitting system of FIG. 1,and performs modulation and equalization for the received data torestore original data.

The digital broadcast receiving system includes a tuner 801, ademodulator 805, an equalizer 803, a known data detector/generator 804,an enhanced decoder 805, a data deinterleaver 806, an RSdecoder/non-systematic RS parity remover 807, and a derandomizer 808.

Also, the digital broadcast receiving system further includes a maindata packet remover 809, an E-VSB packet deformatter 810, and an E-VSBdata processor 811.

Namely, the tuner 801 serves to tune a particular channel frequency toperform down converting and then outputs it to the demodulator 802 andthe known data detector/generator 804.

The demodulator 802 performs carrier restoring and timing restoring forthe tuned channel frequency to generate a base band signal and thenoutput it to the equalizer 803 and the known data detector/generator804.

The equalizer 803 compensates distortion in the channel included in thedemodulated signal and then outputs it to the enhanced decoder 805.

Here, the known data detector/generator 804 detects known data place,which is inserted in the transmitting end, from input/output data of thedemodulator 802, and then outputs symbol stream of the known data, whichis generated in the known data place, to the equalizer 803 and theenhanced decoder 805. Here, the input/output data of the demodulator 802are indicative of data before or after performing demodulation. Also,the known data detector/generator 804 outputs information to theenhanced decoder 805, such that enhanced data, which performs additionalencoding through the enhanced decoder 805, can be discriminated from themain data, which does not perform additional encoding, and such that abeginning point of a block of the enhanced encoder core, which isdiscriminated by the Trellis initialization of FIG. 5B, can be notified.

The demodulator 802 enhances its modulation performance using the knowndata symbol stream when performing timing restoration or carrierrestoration. The equalizer 803 enhances its equalization performanceusing the known data. The enhanced decoder 805 identifies the beginningand end of a block and restores data based on the identified result.

Namely, the enhanced decoder 805 performs encoding for main data symbolsand enhanced data symbols, which are outputted from the equalizer 803,to convert them to bytes and then outputs them to the deinterleaver 806.Such processes will be described in detail as follows.

The deinterleaver 806 performs deinterleaving and outputs thedeinterleaving result to the RS decoder/non-systematic RS parity remover807. Here, the deinterleaver 806 performs a reverse operation of thedata interleaver at the transmitting end. When the inputted packet fromthe RS decoder/non-systematic RS parity remover 807 is main data packet,systematic RS decoding is performed. When the inputted packet isenhanced data packet, non-systematic RS parity byte, which is insertedto the packet, is removed and then outputted to the derandomizer 808.

The derandomizer 808 performs derandomizing for output of the RSdecoder/non-systematic RS parity remover 807 and then inserts MPEGsynchronization byte to the front part of each packet to output it,based on 188 byte packet unit, thereto. Here, the derandomizer 808operates a reverse operation of the randomizer.

The derandomizer 808 outputs its output to a main MPEG decoder (notshown) and the main data packet remover 809, simultaneously. The mainMPEG decoder performs decoding for only packet corresponding to the mainMPEG, since the enhanced data packet is not used in a conventional VSBreceiver or has null or reserved PID. Therefore, the enhanced datapacket is not used in the main MPEG decoder and is thus ignored.

The main data packet remover 809 removes a main data packet of 188 byteunit from the output of the derandomizer 808 and outputs it to the E-VSBpacket deformatter 810. The E-VSB packet formatter 810 removes MPEGheader of 4 bytes from the enhanced data packet which is outputted fromthe main data packet remover 809, in which the MPEG header of 4 bytes isinserted to the enhanced data packet by the E-VSB formatter at thetransmitting end. Also, the E-VSB packet formatter 810 removes bytes towhich place holder (not enhanced data) is inserted at the transmittingend, for example place holders for known data, and then outputs them tothe E-VSB data processor 811. The E-VSB data processor 811 performs areverse operation of E-VSB pre-processor 101 at the transmitting end forthe output of the E-VSB packet deformatter 810, and then outputsenhanced data.

On the other hand, the data inputted to the enhanced decoder 805 may beany of main data or known data, or enhanced data. Here, the main dataand known data do not undergo additional encoding but only Trellisencoding. Also, the enhanced data undergoes all the additional encodingand Trellis encoding.

When the inputted data are main data or known data (or known data placeholder), the enhanced decoder 805 performs Viterbi decoding for theinputted data or performs hard determination for soft determinationvalue, and then outputs the result thereto. Also, the transmitting endregards RS parity byte and MPEG header byte, which are added to theenhanced data packet at the transmitting end, as main data, and does notperform additional encoding therefor. Therefore, Viterbi decoding isperformed or hard determination is performed for soft determinationvalue, such that the result can be outputted.

On the other hand, when the inputted data is enhanced data, the enhanceddecoder 805 performs soft determination decoding to obtain a softdetermination value, and performs decoding for the soft determinationvalue, such that decoding processes for the enhanced data can becompleted. Here, the decoding for the soft determination value is areverse operation of the enhanced encoder core at the transmitting end.

Here, when the enhanced encoder core includes a 1/2 encoder and a blockinterleaver to perform a reverse operation thereof, the receiving endmust include a block deinterleaver and a 1/2 decoder, as reverselyarranged. In this situation, the block deinterleaver performsdeinterleaving for the received data and then the 1/2 decoder performs1/2 decoding for the deinterleaving result. On the other hand, when theblock interleaver was not used at the transmitting end, the receivingend does not need the block deinterleaver.

Namely, the enhanced decoder 805 performs decoding for the enhanced dataas a decoder whose structure is configured such that a Trellis decoder,a block deinterleaver (optional), and a 1/2 decoder are adjacentlyconnected to each other.

When the Trellis decoder and 1/2 decoder are configured as an enhanceddecoder to output a soft determination value, the soft determinationvalue of the Trellis decoder can assist determination of the 1/2decoder. The 1/2 decoder receiving such assistance of the Trellisdecoder can return its soft determination value to the Trellis decoder,such that it can assist determination of the Trellis decoder. Suchdecoding is referred to as turbo decoding. When the turbo decoding isadopted, the total decoding performance can be enhanced.

There are algorithms to output the soft determination value, such asSoft Output Viterbi Algorithm (SOVA), Sub-optimum Soft output Algorithm(SSA), and Maximum A Posteriori (MAP), etc. Here, from the point of viewof symbol errors, the MAP algorithm is superior to the SOVA algorithm.The MAP algorithm calculates probability in log domain while itsperformance does not decrease, and does not need estimation of noisedistribution.

As the transmitting method of the present invention is described above,when a block is used for initialization of a memory state of the Trellisencoding unit such that the memory of the Trellis encoding unit isreturned from a predetermined state value to another the predeterminedstate value, the receiving end determines a soft determination valueusing algorithms, such as a MAP algorithm or a SOVA, etc., therebyobtaining optimal performance.

As described above, the digital broadcast system and the process methodthereof according to the present invention have advantages in thaterrors hardly occur when enhanced data are transmitted through channelsand they also are compatible with the conventional VSB receivers. Also,the digital broadcast system and the process method thereof can receiveenhanced data without errors through channels in which ghost images andnoise are a serious problem, compared with the conventional VSB system.

Also, as known data are inserted to a particular place in data regionand then transmitted, receiving performance of a receiving system, whosechannel variation is serious, can enhanced.

Especially, the present invention initializes a memory of a Trellisencoder at the beginning part of the known data stream, and performsadditional encoding, based on block coding for the enhanced data at thetransmitting end, using the initialization, thereby increasing itsencoding performance. Also, the receiving end performs softdetermination decoding for enhanced data, which is encoded on the basisof block coding, thereby increasing its decoding performance.

The present invention is more effective as it is applied to portable andmobile receivers whose channels vary significantly. Also, the presentinvention remarkably shows its effect in receivers which requirerobustness against noise.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A digital broadcast transmitter comprising: abyte-bit converter configured to convert enhanced data bytes into bitunits and output enhanced data bits; a first encoder configured toencode each of the enhanced data bits at a code rate of 1/H, wherein His an integer greater than 1; a deinterleaver configured to deinterleaveenhanced data corresponding to the encoded enhanced data bits; aremoving unit configured to remove Reed Solomon (RS) parity data placeholders inserted in pre-determined positions within enhanced datapackets including the deinterleaved enhanced data; a second encoderconfigured to perform non-systematic RS encoding on the enhanced datapackets from which the RS parity data place holders are removed in orderto insert RS parity data in the enhanced data packets; and aninterleaver configured to interleave data in the RS-encoded enhanceddata packets, wherein an output of the interleaver comprises a firstdata group including rows having a length of 207 bytes, wherein an ithrow in the first data group has N consecutive Moving Picture ExpertsGroup (MPEG) header bytes, wherein an input of the interleaver comprisesa second data group including rows having a length of 207 bytes, whereina jth row in the second data group has M consecutive MPEG header bytes,wherein N>M, and wherein i, j, M and N are integers greater than
 1. 2.The digital broadcast transmitter of claim 1, wherein the first datagroup further includes known data sequences.
 3. The digital broadcasttransmitter of claim 2, further comprising: a trellis encoding unitconfigured to trellis encode data in the first data group, wherein thetrellis encoding unit includes at least one memory that is initializedby initialization data in the first data group that is just prior to atleast one of the known data sequences.
 4. A method of processingbroadcast data in a digital broadcast transmitter, the methodcomprising: converting, in a byte-bit converter, enhanced data bytesinto bit units to output enhanced data bits; encoding, in a firstencoder, each of the enhanced data bits at a code rate of 1/H, wherein His an integer greater than 1; deinterleaving, in a deinterleaver,enhanced data corresponding to the encoded enhanced data bits; removing,in a removing unit, Reed-Solomon (RS) parity data place holders insertedin pre-determined positions within enhanced data packets including thedeinterleaved enhanced data; performing, in a second encoder,non-systematic RS encoding on the enhanced data packets from which theRS parity data place holders are removed in order to insert RS paritydata in the enhanced data packets; and interleaving, in an interleaver,data in the RS-encoded enhanced data packets, wherein an output of theinterleaver comprises a first data group including rows having a lengthof 207 bytes, wherein an ith row in the first data group has Nconsecutive Moving Picture Experts Group (MPEG) header bytes, wherein aninput of the interleaver comprises a second data group including rowshaving a length of 207 bytes, wherein a jth row in the second data grouphas M consecutive MPEG header bytes, wherein N>M, and wherein i, j, Mand N are integers greater than
 1. 5. The method of claim 4, wherein thefirst data group further includes known data sequences.
 6. The method ofclaim 5, further comprising: trellis encoding, in a trellis encodingunit, data in the first data group, wherein at least one memory in thetrellis encoding unit is initialized by initialization data in the firstdata group that is just prior to at least one of the known datasequences.
 7. A method of processing broadcast data in a transmitter,the method comprising: inserting header data into enhanced data;randomizing the enhanced data into which the header data are inserted;first encoding the randomized enhanced data to add parity data; secondencoding the first-encoded enhanced data at a code rate of U/C (whereinU<C and wherein U and C are positive integers) by a Low Density ParityCheck (LDPC) scheme; block interleaving the second-encoded enhanceddata; converting bits of the block-interleaved enhanced data to symbolunits; convolutional interleaving the enhanced data converted to thesymbol units; and transmitting a frame including theconvolutional-interleaved enhanced data and known data.
 8. The method ofclaim 7, wherein the frame further includes main data multiplexed withthe enhanced data.
 9. The method of claim 7, wherein convolutionalinterleaving the enhanced data reorders a sequence of the enhanced databy using a plurality of memory elements and two switching elements. 10.The method of claim 7, wherein the known data are inserted intopredetermined positions of the frame.